I’m building a Node.js application using MongoDB and Mongoose. I have a ‘companies’ collection with the following schema:

// app/schemas/company.js
const AboutScheme = new Schema({
    slogan: String,
    description: String,
});

const CompanySchema = new Schema({
    name: String,
    about: AboutScheme,
    status: String,
    user: ObjectId,
    email: String
});

I’m creating a POJO class to represent a company document. I want this class to handle its own methods and delegate other methods to the underlying Mongoose document.

// app/domains/company.js

class Company {
    constructor(document) {
        this.#document = document;
    }
    
    sendEmail() {
        console.log('sending email...');
    }
    
    toJSON() {
        return this.#document.toObject();
    }
}

The idea is to separate data logic from business logic. But do it transparently for the user:

const CompanyModel = mongoose.model('Company');
const companyDocument = CompanyModel.findOne({ email: '[email protected]' });
const company = new Company(companyDocument);
company.sendEmail(); // handled by Company class

company.name = 'New Name'; // delegated to this.#document
company.about.slogan = 'new slogan'; // deegated to this.#document

company.save(); // delegated to this.#document

I’m trying to use a Proxy to achieve this transparent delegation, but I’m facing some issues. This doesn’t give me access to this.#document and doesn’t have the effect of modifying properties within the document when saving (this.#document.about.slogan) among other issues.

class Company {
  #document;
    
  constructor(document) {
    this.#document = document;
        
    return new Proxy(this, {
      get(target, name, receiver) {
        if (self[name]) {
          return self[name];
        }

        return Reflect.get(target, name, receiver);
      },
      set(target, name, value, receiver) {
        return Reflect.set(target, name, value, receiver);
      }
    });
  }
}

Can you help me implement a solution that effectively separates data logic from business logic?